ABO PRACTICE EXAM SCRIPT SOLVED
QUESTIONS AND COMPLETE SOLUTIONS
◉ What is the ABO blood group system known for?
Answer: It is the only system where antibodies are consistently and
predictably present in the serum of normal individuals whose red
cells lack the antigens.
◉ What can cause life-threatening hemolytic transfusion reactions?
Answer: ABO mismatch, which can occur after only 10-15 mL of
incompatible blood.
◉ What is the foundation for all pre-transfusion tests?
Answer: ABO compatibility between donor cells and patient serum.
◉ At what gestational age can ABO antigens be detected in embryos?
Answer: As early as 5 to 6 weeks.
◉ When do newborns exhibit fully developed ABO antigens?
Answer: Full expression occurs at about 2 to 4 years of age.
, ◉ Which genes influence the occurrence and location of ABO
antigens?
Answer: ABO, H, and Se genes.
◉ On which chromosome are the ABO genes located?
Answer: Chromosome 9.
◉ What is the role of the H gene in ABO antigen expression?
Answer: It codes for a glucosyltransferase enzyme that adds the
immunodominant sugar to the terminal sugar of the oligosaccharide
chain.
◉ What is the genetic pathway for the A antigen?
Answer: The A gene adds N-acetylgalactosamine to the H antigen.
◉ What does the B gene add to the H antigen?
Answer: D-galactose.
◉ What is the significance of the O gene in the ABO blood group?
Answer: It is amorphic and codes for nothing, resulting in no further
additions to the H antigen.
QUESTIONS AND COMPLETE SOLUTIONS
◉ What is the ABO blood group system known for?
Answer: It is the only system where antibodies are consistently and
predictably present in the serum of normal individuals whose red
cells lack the antigens.
◉ What can cause life-threatening hemolytic transfusion reactions?
Answer: ABO mismatch, which can occur after only 10-15 mL of
incompatible blood.
◉ What is the foundation for all pre-transfusion tests?
Answer: ABO compatibility between donor cells and patient serum.
◉ At what gestational age can ABO antigens be detected in embryos?
Answer: As early as 5 to 6 weeks.
◉ When do newborns exhibit fully developed ABO antigens?
Answer: Full expression occurs at about 2 to 4 years of age.
, ◉ Which genes influence the occurrence and location of ABO
antigens?
Answer: ABO, H, and Se genes.
◉ On which chromosome are the ABO genes located?
Answer: Chromosome 9.
◉ What is the role of the H gene in ABO antigen expression?
Answer: It codes for a glucosyltransferase enzyme that adds the
immunodominant sugar to the terminal sugar of the oligosaccharide
chain.
◉ What is the genetic pathway for the A antigen?
Answer: The A gene adds N-acetylgalactosamine to the H antigen.
◉ What does the B gene add to the H antigen?
Answer: D-galactose.
◉ What is the significance of the O gene in the ABO blood group?
Answer: It is amorphic and codes for nothing, resulting in no further
additions to the H antigen.
